JPH08265085A - Higher harmonic current suppression filter - Google Patents

Abstract

PURPOSE: To prevent resonance between a capacitor for eliminating normal mode noise and a choke coil for suppressing a high frequency current by connecting a resistor in parallel with the choke coil. CONSTITUTION: A resistor R is connected in parallel with a choke coil L being a component of a high frequency current suppression filter 15. Since a pass time of an input current mainly at a low frequency band received from an AC power supply 1 to a power supply device 2 is extended, a peak of the input current is decreased and its higher harmonic components is suppressed. Furthermore, a capacitor Cx in the power supply device 2 absorbs and eliminates the normal mode noise of a symmetrical component generated between power supply lines 4, 4A. In this case, the series resonance by the capacitor Cx and the choke coil L is not caused by the resistor R connected across choke coil L and a satisfactory higher harmonic suppression effect by the higher harmonic current suppression filter 15 is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a harmonic current suppressing filter which is provided in the preceding stage of an electronic device and has a choke coil for suppressing harmonic current inserted and connected to a power supply line.

[0002]

2. Description of the Related Art Generally, in the case of various electronic devices equipped with a capacitor input type rectifier circuit, the input voltage flows only during a period when the input voltage from the AC power source is higher than the voltage between the terminals of the capacitor. The peak value becomes extremely large near the maximum value of the input voltage, and it contains harmonic currents exceeding the standard. As a means for avoiding such itself, an active filter having a boost converter on the output side of the rectifier circuit is incorporated in the power supply device,
Japanese Patent Application Laid-Open No. 2-84069 discloses that an input current approaches a sine wave waveform that is substantially the same as the input voltage. However, since such an active filter has a switching element and the like, the circuit configuration is complicated, resulting in high cost, and there is also a problem that it cannot be directly incorporated in an existing device.

On the other hand, there is a method of inserting and connecting a so-called harmonic current suppressing choke coil that effectively suppresses the harmonic current into the power supply line from the AC power supply to the electronic equipment. The harmonic current suppression filter having such a choke coil has the advantages that the circuit configuration is extremely simple and that it can be externally attached directly to the front stage of the electronic device.

[0004]

In the above-mentioned prior art, commercially available standard switching power supplies, which are electronic devices, include capacitors for removing normal mode noise (across the line) between power supply lines, including custom-made power supplies.・ Equipped with a line capacitor). To illustrate this more concretely with FIG. 4, 1 is a commercial AC power supply, 2 is a power supply device, and immediately after the input terminals 3 and 3A of the power supply device 2, there is a normal mode noise between the power supply lines 4 and 4A. The removal capacitor Cx is connected. Further, in front of the power supply device 2, there is provided a harmonic current suppression filter 5 in which a choke coil L for suppressing harmonic current is inserted and connected to one power supply line 4. Although not shown, a diode bridge as an input rectifying circuit is provided in the subsequent stage of the capacitor Cx. However, in such a circuit configuration, the capacitor Cx provided inside the power supply device 2,
Due to the series resonance phenomenon with the choke coil L, there is a problem that a satisfactory harmonic suppression effect cannot be obtained.

In view of the above problems, the present invention provides a harmonic current suppressing filter which can easily prevent the resonance phenomenon between the normal mode noise removing capacitor and the high frequency current suppressing choke coil. The purpose is to do.

[0006]

A high-frequency current suppression filter according to the present invention is provided in the front stage of an electronic device in which a capacitor for removing normal mode noise is connected between power supply lines, and a high-frequency current suppression filter is provided in the power supply line for suppressing harmonic currents. In a harmonic current suppressing filter having a choke coil inserted and connected, a resistor is connected in parallel with the choke coil.

[0007]

According to the above construction, since the choke coil prolongs the passage time of the input current mainly in the low frequency range taken into the electronic equipment, the peak value of the input current becomes small and the harmonic component thereof is suppressed. It Moreover, the normal mode noise of the symmetrical component generated between the power supply lines is absorbed and removed by the capacitor in the electronic device. In this case, due to only one resistor connected to both ends of the choke coil, the series resonance phenomenon due to the capacitor and the choke coil does not occur, and a satisfactory harmonic suppression effect can be obtained.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. The same parts as those shown in FIG. 4 shown in the above-mentioned conventional example are designated by the same reference numerals, and detailed description of the common parts is omitted. In FIG. 1 showing a circuit diagram, the present embodiment is different from the conventional example in that a resistor R is connected in parallel with a choke coil L constituting a harmonic current suppressing filter 15.
The other points are exactly the same as the circuit diagram shown in FIG.

In the configuration shown in FIG. 1, the choke coil L of the harmonic current suppressing filter 15 increases the passage time of the input current mainly in the low frequency range taken from the AC power supply 1 into the power supply device 2, so that the input current The peak value becomes small and the harmonic component is suppressed. Further, the capacitor Cx in the power supply device 2 absorbs and removes the normal mode noise of the symmetrical component generated between the power supply lines 4 and 4A. In this case, the series resonance phenomenon due to the capacitor Cx and the choke coil L does not occur due to only one resistor R connected to both ends of the choke coil L, and the harmonic current suppressing filter 15 provides a satisfactory harmonic suppressing effect. Will be able to.

Next, a comparison between the harmonic current suppressing filter 15 in this embodiment and the conventional harmonic current suppressing filter 5 will be described from the measured data shown in FIGS. 2, 3, 5 and 6. . It should be noted that these actual measurement data are experimentally obtained based on the circuit configuration of FIG. 1 or 4. The measurement conditions used an AC power supply 1 of 200 V / 50 Hz and a power supply device 2 of 100 W of input power having a capacitor Cx of 0.68 μF, and the harmonic current suppression filter 5 of the conventional example used 34 mH. The choke coil L is connected to the choke coil L. In addition to the choke coil L of 34 mH, the resistor R of 200 Ω is connected in parallel to the choke coil L in the harmonic current suppressing filter 15 of this embodiment.

FIG. 2 is a harmonic current suppression filter of this embodiment.
FIG. 5 shows the waveform of the input current of the power supply device 2 according to the reference numeral 15, and FIG. 5 shows the waveform of the input current of the power supply device 2 according to the conventional harmonic current suppression filter 5. As is clear from these measured data, it is understood that the current waveform in FIG. 5 has an undesirable ripple A due to the series resonance phenomenon between the capacitor Cx and the choke coil L. On the other hand, FIG.
Similar ripples are hardly generated in the current waveform of.

On the other hand, FIG. 3 shows the measured data of the harmonic current by the harmonic current suppressing filter 15 of this embodiment, and FIG. 6 shows the measured data of the harmonic current by the conventional harmonic current suppressing filter 5. All of these are performed based on the IEC555-2 standard. As is clear from each measured data, in the graph of FIG. 6 of the conventional example, the series resonance phenomenon of the capacitor Cx and the choke coil L causes the 17th to 23rd harmonic current B to satisfy the standard. It turns out that the limit value of is exceeded. On the other hand, in the graph of FIG. 3 in the present embodiment, the 17th to 23rd harmonic currents are also improved below the limit value, which is a value that satisfies the standard.

As described above, in the above embodiment, the choke coil L for suppressing the harmonic current is provided in the front stage of the electronic device to which the capacitor Cx for removing the normal mode noise is connected and which is provided in the power supply line 4. By simply connecting the resistor R to the connected harmonic current suppression filter 15 in parallel with the choke coil L, the advantages of the conventional harmonic current suppression filter 15 can be fully utilized and the capacitor Cx
It is possible to easily prevent a resonance phenomenon between the choke coil L and the choke coil L. In this case, the harmonic current suppression filter 15
Is externally connected to the front stage of the power supply device 2, so that the resistor R can be easily added to the inside of the power supply device 2 without any modification. Therefore, the above effect can be easily achieved even with respect to the existing power supply device 2.

The present invention is not limited to the above embodiment, but various modifications can be made within the scope of the gist of the present invention. The harmonic current suppression filter of the present invention is not limited to the power supply device shown in the embodiments, but can be provided in the front stage of various electronic devices. Further, the constants of the choke coil and the capacitor may be appropriately changed based on the actual measurement data shown in the accompanying drawings so as to obtain the most desirable characteristics.

[0015]

The harmonic current suppressing filter of the present invention is provided in the preceding stage of an electronic device in which a capacitor for removing normal mode noise is connected between power supply lines, and a choke coil for suppressing harmonic current is provided in the power supply line. In the harmonic current suppression filter that is inserted and connected, a resistor is connected in parallel with the choke coil, and the resonance phenomenon between the capacitor for removing normal mode noise and the choke coil for suppressing harmonic current is simplified. It becomes possible to prevent it.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

FIG. 2 is a waveform diagram showing an actual measurement value of an input current in the present embodiment.

FIG. 3 is a graph showing the measured values of harmonic currents in this example.

FIG. 4 is a circuit diagram showing a conventional example.

FIG. 5 is a waveform diagram showing measured values of input current in a conventional example.

FIG. 6 is a graph showing measured values of harmonic currents in a conventional example.

[Explanation of symbols]

 2 Power supply device (electronic equipment) 4, 4A Power supply line 15 Harmonic current suppression filter Cx capacitor L Choke coil R Resistance

Claims (1)

[Claims] 1. A harmonic current suppressing filter which is provided in a front stage of an electronic device in which a capacitor for removing normal mode noise is connected between power supply lines, and a choke coil for suppressing harmonic current is inserted and connected to the power supply line. 3. A harmonic current suppressing filter according to, wherein a resistor is connected in parallel with the choke coil.